1. Field of the Invention
The present invention relates to an apparatus which comprises a communication unit having host and client modes, and can transmit image data to another device.
2. Description of the Related Art
Conventionally, an image captured by an image capturing apparatus such as a digital camera is transmitted to another device such as a computer or digital camera which is connected to the image capturing apparatus by wire or wirelessly.
For example, there is known an apparatus which compares a captured image with owner information of an external device, and when they match each other, wirelessly transmits the captured image to the external device (see Japanese Patent Laid-Open No. 2005-252457).
As a communication means used at this time, a method compliant with a communication interface standard such as USB (Universal Serial Bus) or IEEE1394 is popular at present.
A method compliant with a wireless LAN standard such as IEEE802.11b or IEEE802.11g is also sometimes used.
The use of a method compliant with a WUSB (Wireless Universal Serial Bus) standard for wirelessly using a USB has also been examined.
Some of these interfaces, as typified by the USB and WUSB, define the relation between two devices in the physical layer. For example, when connecting digital cameras using a USB, it is necessary to define one digital camera as a USB host and the other as a USB device.
According to the On-The-Go standard established as part of the USB standard, a cable having a Mini-A plug and Mini-B plug at two ends is defined as a cable for connecting devices having USB interfaces. When this cable is used, a device to which the Mini-A plug is connected serves as a USB host upon connection, and a device to which the Mini-B plug is connected serves as a USB device. Hence, when connecting digital cameras using a USB-compliant communication unit, the cable is connected to determine one serving as a USB host and the other serving as a USB device.
For example, an image processing apparatus disclosed in Japanese Patent Laid-Open No. 2004-40370 pertains to a technique of connecting digital cameras using a USB-compliant communication means to transmit/receive an image file.
Even according to the WUSB, it is necessary to define one of digital cameras as a WUSB host and the other as a WUSB device. In other words, when the user connects digital cameras via a WUSB, he needs to activate one of them as a WUSB host and the other as a WUSB device.
For example, even when transmitting image data captured by a digital camera to another connected digital camera, one of them operates in the host mode, and the other operates in the client mode. For example, when digital cameras are connected by a communication interface which defines the association between two devices in the physical layer, as typified by the USB and WUSB, it is necessary to operate one of the digital cameras in the host mode and the other in the client mode. In this case, it is necessary to determine which of the digital cameras operates in the host mode.
This also applies to a case where three or more digital cameras transmit captured image data to the remaining connected digital cameras. That is, when digital cameras are connected by a communication interface which defines the association between devices in the physical layer, it is necessary to operate one of the digital cameras in the host mode and the remaining digital cameras in the client mode. At this time, the digital cameras in the client mode cannot directly transmit image data to each other.
The technique disclosed in Japanese Patent Laid-Open No. 2005-252457 does not consider connection of devices by a communication interface, such as a USB or WUSB, which defines the association between two devices in the physical layer. A mechanism for determining which of devices changes into the host mode needs to be separately arranged. For example, the user needs to assign the host and client modes to devices.
When the technique disclosed in Japanese Patent Laid-Open No. 2005-252457 is applied to three or more devices connected by a communication interface which defines the association between devices in the physical layer, a device in the host mode needs to relay data exchange between devices in the client mode, complicating the configuration.
According to the technique disclosed in Japanese Patent Laid-Open No. 2004-40370, the user needs to operate a master camera to switch between the host and client modes. Also, the user cumbersomely needs to designate image data to be transmitted to a connected device.